The better known biometric markers currently used to identify people include analysis and comparison of facial features, irides, fingerprints, hand and palm prints, and wrist and finger pad blood vessels. Other biometric factors include analysis and comparison of gait, ear contour and DNA.
No one biometric parameter to date has proven to be perfectly accurate and practical across the entire human cohort. For example, the accuracy of facial feature recognition can vary significantly with changes in illumination. Five percent of the population has unreadable fingerprints, either being congenitally blurred or effectively removed through manual labour. In the United Kingdom, seven percent of the population failed to enroll in an iris recognition system. While DNA analysis is accurate, it is highly technical and there are generally lengthy delays before a result is known.
Another biometric that is highly unique and slowly time varying is the shape of the cornea—that is the dome like lens at the front of the eye. Currently the shape of the cornea is measured for clinical purposes using a corneal topographer; such as the Medmont E300 topographer. These machines use an illuminated series of concentric rings (known as a Placido disc) as a target source. One eye gazes directly at this illuminated target and an image is reflected from the pre-corneal tear film. By means of processing software, the reflected image is converted into a topographic map of the cornea representing the corneal contours.
U.S. 60/661,961 (Dixon et al) describes the use of gaze tracking and corneal ‘surface irregularities’ and ‘discernable features’ to define a unique biometric.
The use of the cornea as a biometric for identification is described in U.S. 60/685,484 (Mason). This system operates by capturing an image of at least part of the cornea and then deriving one or more ‘geometric’ parameters in respect to each of plural locations on the cornea; these parameters include measures of curvature, corneal height, refractive power, thickness and others. Authentication is then performed by comparing these parameters with previously derived parameters at the corresponding locations of a reference cornea.